Darcs.Util.ByteString

GZIp and MMap IO for ByteStrings, encoding utilities, and miscellaneous functions for Data.ByteString

Documentation

unsafeWithInternals :: ByteString -> (Ptr Word8 -> Int -> IO a) -> IO a

Do something with the internals of a PackedString. Beware of altering the contents!

unpackPSFromUTF8 :: ByteString -> String

Decodes a ByteString containing UTF-8 to a String. Decoding errors are flagged with the U+FFFD character.

packStringToUTF8 :: String -> ByteString

gzReadFilePS :: FilePath -> IO ByteString

Read an entire file, which may or may not be gzip compressed, directly into a ByteString.

mmapFilePS :: FilePath -> IO ByteString

Like readFilePS, this reads an entire file directly into a ByteString, but it is even more efficient. It involves directly mapping the file to memory. This has the advantage that the contents of the file never need to be copied. Also, under memory pressure the page may simply be discarded, wile in the case of readFilePS it would need to be written to swap. If you read many small files, mmapFilePS will be less memory-efficient than readFilePS, since each mmapFilePS takes up a separate page of memory. Also, you can run into bus errors if the file is modified. NOTE: as with readFilePS, the string representation in the file is assumed to be ISO-8859-1.

gzWriteFilePS :: FilePath -> ByteString -> IO ()

gzWriteFilePSs :: FilePath -> [ByteString] -> IO ()

gzReadStdin :: IO ByteString

Read standard input, which may or may not be gzip compressed, directly into a ByteString.

gzWriteHandle :: Handle -> [ByteString] -> IO ()

type FileSegment = (FilePath, Maybe (Int64, Int))

Pointer to a filesystem, possibly with start/end offsets. Supposed to be fed to (uncurry mmapFileByteString) or similar.

readSegment :: FileSegment -> IO ByteString

Read in a FileSegment into a Lazy ByteString. Implemented using mmap.

isGZFile :: FilePath -> IO (Maybe Int)

gzDecompress :: Maybe Int -> ByteString -> ([ByteString], Bool)

Decompress the given bytestring into a lazy list of chunks, along with a boolean flag indicating (if True) that the CRC was corrupted. Inspecting the flag will cause the entire list of chunks to be evaluated (but if you throw away the list immediately this should run in constant space).

dropSpace :: ByteString -> ByteString

breakSpace :: ByteString -> (ByteString, ByteString)

linesPS :: ByteString -> [ByteString]

unlinesPS :: [ByteString] -> ByteString

This function acts exactly like the Prelude unlines function, or like Data.ByteString.Char8 unlines, but with one important difference: it will produce a string which may not end with a newline! That is:

unlinesPS ["foo", "bar"]

evaluates to "foo\nbar", not "foo\nbar\n"! This point should hold true for linesPS as well.

TODO: rename this function.

hashPS :: ByteString -> Int32

breakFirstPS :: Char -> ByteString -> Maybe (ByteString, ByteString)

breakLastPS :: Char -> ByteString -> Maybe (ByteString, ByteString)

substrPS :: ByteString -> ByteString -> Maybe Int

readIntPS :: ByteString -> Maybe (Int, ByteString)

readIntPS skips any whitespace at the beginning of its argument, and reads an Int from the beginning of the PackedString. If there is no integer at the beginning of the string, it returns Nothing, otherwise it just returns the int read, along with a B.ByteString containing the remainder of its input.

isFunky :: ByteString -> Bool

fromHex2PS :: ByteString -> ByteString

fromPS2Hex :: ByteString -> ByteString

betweenLinesPS :: ByteString -> ByteString -> ByteString -> Maybe ByteString

betweenLinesPS returns the B.ByteString between the two lines given, or Nothing if they do not appear.

breakAfterNthNewline :: Int -> ByteString -> Maybe (ByteString, ByteString)

breakBeforeNthNewline :: Int -> ByteString -> (ByteString, ByteString)

intercalate :: ByteString -> [ByteString] -> ByteString

O(n) The intercalate function takes a ByteString and a list of ByteStrings and concatenates the list after interspersing the first argument between each element of the list.

isAscii :: ByteString -> Bool

Test if a ByteString is made of ascii characters

decodeLocale :: ByteString -> String

Decode a ByteString to a String according to the current locale unsafePerformIO in the locale function is ratified by the fact that GHC 6.12 and above also supply locale conversion with functions with a pure type. Unrecognized byte sequences in the input are skipped.

encodeLocale :: String -> ByteString

Encode a String to a ByteString according to the current locale

decodeString :: String -> IO String

Take a String that represents byte values and re-decode it acording to the current locale. Note: we globally enforce char8 as the default encoding, see Main and Darcs.Utils. This means we get command line args and environment variables as Strings with char8 encoding, too. So we need this to convert such strings back to the user's encoding.